Device for promoting the formation of bone substance

ABSTRACT

A splint for fixing a bone structure in position is in the form of a marrow nail, of which at least a part is constructed to serve as an electrode. The electrode is connected to a first terminal end of a pick-up coil. The second terminal end of the coil is connected to a second electrode which may be also attached to the marrow nail or is fixed to a belt-like carrier adapted to be tightened around the bone structure.

United States Patent 1191 Kraus et al.

[ June 28, 1974 DEVICE FOR PROMOTING THE C FORMATION OF BONE SUBSTANCE Foreign Application Priority Data Apr. 6, I97] Germany.... 21 I686) us. 01. 128/82.l, 3/1 Int. Cl. A6ln Fieldof Search 128/821, 92; 3/1 1 References Cited UNITED STATES PATENTS 11/1971 Bokros l28/9 2 B1 6/1972 Bosacco 128/92 D OTHER PUBLICATIONS Effects of Electric Currents on Bone in Vivo, by Bassett et al., Nature, Nov. 14, 1964, pp. 652-654.

The Effect of Direct Current 0n Bone, by F riedenberg et al., Surgery, Gynecology & Obstetrics, July, 1968, pp. 97-102.

Bioelectric Potentials in Bone, by Friedenberg et al., Journal of Bone & Joint Surgery, July, 1966, pp. 915-923.

Primary ExaminerRichard A. Gaudet Assistant ExaminerJ. Yasko Attorney, Agent, or Firm-Spencer & Kaye [571 ABSTRACT A splint for fixing a bone structure in position is in the fonn of a marrow nail, of which at least a part is con- 1 structed to serve as an electrode. The electrode is connected to a first terminal end of a pick-up coil. The second terminal end of the coil is connected to a sec- 0nd electrode which may be also attached to the marrow nail or is fixed to a belt-like carrier adapted to be tightened around the bone structure.

129 13; REQWJPA JEEEQ PATENTED JUN? 8 I974 SHEET 5 0F 6 Fig.10b

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PATENTEDJUN28 I974 sum 6 or 6 Fig.1]

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REFERENCE TO COPENDING APPLICATION The present application describes a further develop ment of the invention described in Application Ser. No. 26,809,, now US. Pat. No. 3,745,995, issued July 17, I973.

BACKGROUND OF INVENTION 1. Field to which invention relates The present invention relates to a device for promting the formation of bone substance adjacent to the bone of a living organism, comprising a splint for fixing the bone in position and provided with at least one pick-up coil, whose two terminal ends are connected with at least one electrode adapted for application to the bone structure.

2. The prior art The fixing in position of a broken bone by means of a splint with a metal plate screwed onto the outer surface of the bone has the disadvantage that the metal plate brings about an unnatural distribution of forces in the bone during healing and this may lead to refracture of the bone. The plate screwed on the bone practically cuts out the curative physiological stress and load on the bone during healing. Since at the present time comminuted fractures are becoming more and more numerous, it is often no longer possible to fix small bone fragments in position by means of plates and screws so that as a result osteogenesis is rendered uncertain.

Therefore, for some time a so-called Kiintscher or marrow nail has been employed which is inserted into a hole bored into the marrow cavity. The endosteum and the blood vessels contained in it are destroyed in this method so that the healing process is delayed. As a result in the case of multiple or chip fractures such a marrow nail can be used only to a very limited extent as it does not support the small bone fragments in the case of such chip fractures. Although there has been a previous proposal to fix such cips in position by socalled cerclages, that is to say by means of wires which are laid around the chips and then drawn together, the

substantial forces exerted by the wires on the bone lead to a contraction of the periosteum and block the blood vessels contained in it. Such wire cerclages cannot ensure that proper osteosynthesis takes place.

SUMMARY OF INVENTION invention the part of the marrow nail serving as an electrode is provided with at least one counter-electrode, which is arranged on a belt-like carrier, which has a closure'whieh enables it to exert a circumferential force on the bone or its part into which the marrow nail has been introduced.

Further developments of the invention will be described in what follows.

LIST OF SEVERAL VIEWS OF DRAWINGS Embodiments of the invention will now be described with reference to the accompanying drawings in more detail.

FIG. 1 shows a marrow nail inserted into a broken bone, in accordance with one embodiment of the invention.

FIG. 2 shows a marrow nail arranged in a fractured bone in accordance with a second embodiment of the invention.

FIG. 3 shows a partly cut-away view of the marrow nail in accordance with FIG. 2.

FIG. 4 is a partial view of a fractured bone with a device in accordance with a further embodiment of the invention.

FIG. 5 is a plan view of a pick-up coil of the device in accordance with FIG. 4.

FIG. 6 shows on an enlarged scale the zone denoted Z in FIG. 4.

FIG. 7a is a view of a cerclage for a device of the type indicated in FIG. 4.

FIG. 7b is a front view of the fastener used with the cerclage of FIG. 7a.

FIG. 7c is a side view of the fastener of FIG. 7b.

FIG. 7d is a side view of a counter-electrode of FIG.

FIG. 8 is a perspective view of a cerclage in accordance with FIG. 7 arranged on a fractured bone.

FIG. 9 shows a cross-section of the arrangement shown in FIG. 8.

FIGS. 10a and 10b show part of a hip-joint prosthesis from the broad and narrow sides respectivelylin accordance. with an embodiment of the invention.

FIGS. 1 la and 11b are views generally corresponding to FIGS. 10a and 10b of a further embodiment in accordance with the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS As an example of a fractured bone FIG. I shows a fractured human femur, which is fixed in position by means of a Kt'mtscher or marrow nail 14 inserted into the marrow cavity 12 which has been bored out. The

marrow nail 14 is made in a conventional manner of a piece of sheet metal of cobalt-chrome alloy, which is bent so as to have the shape of a slotted tube. A middle section of the marrow nail is provided with insulating material 16, on which two wire or strip-like electrodes 18 and 20 are arranged. The electrodes are preferably placed on opposite sides of the marrow nail adjacent to the fractures 22. They are connected with the ends of a wire winding of a pick-up coil 24, which is arranged on a magnetic core 26 inside the marrow nail l4. During treatment of the patient the pick-up coil is placed in an alternating magnetic field, which is produced by means of a cylindrical coil 28 for example, as described in patent application Ser. No. 26,809, now US. Pat. No. 3,745,995 issued on July I7, 1973 to Werner Kraus. In particular the alternating magnetic field should have a low frequency, for example up to approximately 60 Hz and its pulses should not have steep flanks.

FIG. 2 shows a further embodiment of a marrow nail in accordance with the invention. This marrow nail 14 again has an insulated section 16', on which two substantially semi-cylindrical electrodes 18', 20 are arranged which are insulated from each other and from the actual marrow nail 14'. The electrodes have electrically conducting surfaces, which extend over the greater part of the length of the marrow nail l4.

The marrow nail 14 itself is tubular and consists of a non-ferromagnetic material. In its interior a pickup coil 24' is arranged and the ends of its wire winding are connected with the electrodes 18 and 20 respectively.

In the case of the embodiment in accordance with FIGS. 4, 5, and 6 the whole marrow nail 14" serves as an electrode and cooperates with counter-electrodes 20a to 20d, which are arranged on the outer surface of the fractured bone 10 and are held in position by beltlike straps 30. The marrow nail 14" is connected via a conductor 32 with the one terminal of a pick-up coil 24", whose other terminal is connected with the electrodes a and 20d via suitable lines. The pick-up coil 24" is shown in plan view in FIG. 5. It can be embedded in a fastener 34, which serves to hold together the overlapping ends of the belt'like straps 30. Preferably the straps 30 are ribbed on both sides as is shown in FIG. 6, so that firstly a slipping of the overlapping ends in relation to each other is prevented and secondly vessels, which run between the straps 30 and the bone 10, can slip into the grooves between the ribs and are not pinched. FIG. 7 shows a further embodiment of a beltlike electrode carrier. The electrode carrier constructed in the form of a cerclage consists of a part 40.

of a plastics material, for example polytetrafluoroethylene, which can be reinforced by wires or glass fibers. The part 40 of the plastics material has a relatively broad initial part 42, which is provided with a hole 44 and cooperates with a fastener 46 in the form of an U-shaped piece of metal sheet, which is held by means of a screw (not shown) extending through the hole 44 and a corresponding hole in the piece of sheet metal 46. The initial part 42 is connected with two narrow belt-like parts 48 which are preferably ribbed in the manner shown in FIG. 6. On the belt-like or straplike parts 48 sliding electrode arrangements 50 are arranged, of which one is shown in section at the bottom of FIG. 7 on the right-hand side. The electrode arrangements 50 comprise the actual electrode 20", which rests in a retaining means 52, made of plastics material, which can be slid on the associated belt-like part 48. As long as the belt-like parts are not under tension the electrode arrangement 50 can be displaced in the longitudinal direction of the belt-like parts 48. When the electrode is tightened the holding means 52 slides into the ribs and the electrode becomes fixed at the position intended.

FIGS. 8 and 9 shows a device in accordance with FIG. 7 tightened around a bone. The pick-up coil 24 connected with the electrodes is fixed in the fastener device 46. It would naturally be possible for the pickup coil to be arranged in the interior of the marrow nail 14 holding the bone in position, as has ben explained with reference to FIGS. 1 and 3.

The marrow nail can also be made of a material which is absorbed by the body. for example animal bone freed of protein. In this case no separate insulating device for bringing about electrical separation of the electrodes would have to be provided.

FIGS. 10 and 11 show two embodiments or marrow nails which form part of hip joint prosthesis, that is to say an artificial human hip-joint.

The hip joint prosthesis in accordance with FIG. 10 is constructed using a conventional cobalt-chrome alloy and includes a substantially spherical head 60, which adjoins the dagger-like shank 62 (FIG. 10) which is inserted in a conventional manner from above into the open marrow cavity to replace the injured or diseased hip-joint in a conventional manner.

The replacement of the head of the femur is carried out more particularly in the case of fractures of the neck of the femur in the case of elderly persons and in advanced cases of Arthrosis deformans, a degenerative joint and bone disease. Up till now the hip joint prosthesis has been fixed in position in the marrow cavity using a particular cement. A substantial disadvantage of this manner of fixation of the prosthesis in the femur resides in that the further decomposition of the bone is not retarded by the replacement metal joint so that in the course of time there is a loss of frictional connection between the bone and the cement. The prosthesis then becomes loose and this leads to impairment of the gait and pain. In the past such protheses have involved a further operation being carried out as a matter of course after some years.

In the case of the hip-joint prothesis in accordance with the invention as shown in FIGS. 10 and 11 the attachment of the prosthesis to the bone substance is promoted by the influence of low frequency alternating currents which gradually vary.

The shank 62 (FIG. 10) forming the marrow nail of the hip-joint prosthesis comprises for this purpose a pickup coil 24, which is preferably provided with a magnetizeable core of magnetically soft material. The shank 62 can for this purpose comprise a channel-like recess whose opening 64 is only shown diagrammatically in FIG. 10. The oneend of the wire winding of the pickup coil is connected with an electrode 18m which is insulated from the shank 62 and is arranged approximately in the center of the shank, while the other end of the wire winding is connectd with two electrodes 18n and 18p, which are insulated from the shank 62 and are arranged at its upper and lower end respectively.

In the case of the embodiment in accordance with FIG. 11 elongated strip-like electrodes are arranged on the two opposite broad sides of the shank 62', only one electrode, 18', being shown in FIG. 11. The electrodes are insulated again from the shank 62' which is made of metal and are connected with the ends of the wire winding of a pick-up coil (not shown) which is accommodated in the shank 62.

Alternatively the shank can itself be used as an electrode and cooperate with counter-electrodes, which are arranged in an insulated fashion in the shank or are located on the cerclages extending round the bone, as was described with reference to FIGS. 4 to 9.

After the hip-joint prosthesis in accordance with FIG. 10 or FIG. 11 has been introduced into the marrow cavity of the femur, alternating currents are induced in the pick-up coil as explained in the abovementioned patent application. These alternating currents encourage the formation of bone and vessels, and newly formed bone substance grows around the shank 62 or 62', respectively, so that a firm fit is ensured. The alternating magnetic field inducing the alternating currents also contributes to bone and vessel formation. For the fixation of the prosthesis therefore at the most only small quantities of cement are necessary.

nail. a

, -This subsequent treatment then brings about growth leading to a firm renewed to the bone.

The shape of .the shank 62 and 62', which has alterattachment of the prosthesis nating expanded and drawn-in parts, encourages a firm attachment in the, marrow cavity of the bone owing to bone growth;

Whatwe claim is: v r v 1. A device for assisting in formation of bone substance adjacentto the bone of a living organism, coinprising: a splint for fixing the boneinposition and-including a marrow nail;'at least one pick-up coil associated with the splint and having two terminals and said coil being adapted to be coupled to a signal generating means for establishing within said vcoil an a.c. current;

, an electrode, assembly connected to said terminals-and adapted to be connected to the bone; and, the marrow nail having an elongated main part on which there is embeddedalong one surface thereof at least a portion of the electrode assembly which is insulated at least a with respect to the main part and has an exposed electrically conducting surface.

2.vAdevice in accordance with claim 1, wherein the electrode, assembly includes two electrodes, insulated from each other, and embedded in opposite sides of the main part.

3. A device in accordance with claim 2,in whichthe electrodes have elongated surfaces, which run along he-longitudinal axisof the main part of the marrow 1 [4. A device in accordance with claim 1, wherein the nail, which is made of non-magnetic material.

5. A device in accordance with claim 1, wherein the marrow nail forms a part of a femur prosthesis and at therend has a hip-joint femurfhead, or a femur neck prosthesis V v 6. device in accordance with claim Sywherein the marrow nail has alternating expanded and drawn-in "portions along its longitudinal axis.

7. A device for assisting information of bone substance adjacent to the bone of a living organism, comprising: a splint for fixing the bone in position and including a marrow nail; at least one pick-up coil associated with the splint and having two terminals and said coil being adapted to be coupled to a signal generating means for establishing within said coil an ac. current;

an electrode assembly connected to said terminals and adapted to be connected to the bone; and, at least a portion of the marrow nail forming at least a portion of the electrode assembly; wherein the electrode assembly includes at least one counter-electrode which is mounted on a belt-like carrier, the part of the marrow nail forming a portion of the electrode assembly is adapted to cooperate with said counter-electrode, and

, the carrier includes a fastener for tightening it around the fractured bone encompassing the marrow nail.

8. A device in accordance with claim 7, wherein that I the belt-like carrier comprises a straplike part which on .both sides is ribbed in the transverse direction,

, 9. A device in accordance with claim 7, wherein the carrier has a broad initial part adapted to cooperate "with the fastener and this broad part adjoins two nar "row strap-like parts which are spaced apart.

10. A device in accordance with claim 7, wherein the pick-up coil is accommodated in the fastener.

l 1. A-device in'acco'rdance with claim 7, wherein the counter electrode is arranged on the belt-like carrier so pick-up coil is arranged in the main part of the marrow that it can be slid along the longitudinal axis of the carrier. v I

12. A device in accordance with claim 1, wherein the electrode assembly includes a plurality of electrodes which are arranged spaced apart along the longitudinal axis of the marrow'nail. 

1. A device for assisting in formation of bone substance adjacent to the bone of a living organism, comprising: a splint for fixing the bone in position and including a marrow nail; at least one pick-up coil associated with the splint and having two terminals and said coil being adapted to be coupled to a signal generating means for establishing within said coil an a.c. current; an electrode assembly connected to said terminals and adapted to be connected to the bone; and, the marrow nail having an elongated main part on which there is embedded along one surface thereof at least a portion of the electrode assembly which is insulated at least with respect to the main part and has an exposed electrically conducting surface.
 2. A device in accordance with claim 1, wherein the electrode assembly includes two electrodes, insulated from each other, and embedded in opposite sideS of the main part.
 3. A device in accordance with claim 2, in which the electrodes have elongated surfaces, which run along the longitudinal axis of the main part of the marrow nail.
 4. A device in accordance with claim 1, wherein the pick-up coil is arranged in the main part of the marrow nail, which is made of non-magnetic material.
 5. A device in accordance with claim 1, wherein the marrow nail forms a part of a femur prosthesis and at the end has a hip-joint femur head, or a femur neck prosthesis.
 6. A device in accordance with claim 5, wherein the marrow nail has alternating expanded and drawn-in portions along its longitudinal axis.
 7. A device for assisting in formation of bone substance adjacent to the bone of a living organism, comprising: a splint for fixing the bone in position and including a marrow nail; at least one pick-up coil associated with the splint and having two terminals and said coil being adapted to be coupled to a signal generating means for establishing within said coil an a.c. current; an electrode assembly connected to said terminals and adapted to be connected to the bone; and, at least a portion of the marrow nail forming at least a portion of the electrode assembly; wherein the electrode assembly includes at least one counter-electrode which is mounted on a belt-like carrier, the part of the marrow nail forming a portion of the electrode assembly is adapted to cooperate with said counter-electrode, and the carrier includes a fastener for tightening it around the fractured bone encompassing the marrow nail.
 8. A device in accordance with claim 7, wherein that the belt-like carrier comprises a straplike part which on both sides is ribbed in the transverse direction.
 9. A device in accordance with claim 7, wherein the carrier has a broad initial part adapted to cooperate with the fastener and this broad part adjoins two narrow strap-like parts which are spaced apart.
 10. A device in accordance with claim 7, wherein the pick-up coil is accommodated in the fastener.
 11. A device in accordance with claim 7, wherein the counter electrode is arranged on the belt-like carrier so that it can be slid along the longitudinal axis of the carrier.
 12. A device in accordance with claim 1, wherein the electrode assembly includes a plurality of electrodes which are arranged spaced apart along the longitudinal axis of the marrow nail. 